Red and black beetles living in a typical backyard garden are usually box elder bugs or lady birds. Neither are particularly harmful to plants, although both are considered nuisances if they find their way into homes. Box elder bugs can become a garden problem in years with high populations of this insect. Lady bird beetles are welcomed by gardeners because of their use as a natural pest controller.
Box elder bugs are insects with thin bodies about ½-inch long, primarily black with three red lines on the thorax, one red line on each side, and one on each wing.
Ladybug beetles have a number of differing colour variations. They are generally round or oval in shape and range from 3 to 7 millimetres in size, depending on the species.
Box Elder Habits
These insects are found in spring and early summer around trees whose name they bear, feeding on sap and seeds. During years when the population is higher, they might cause damage to fruit trees because of their sap-consuming habits. Box elder bugs migrate to the ground in late summer to begin their search for a place to overwinter. This is the time when they might be found on garden plants, but they generally don't stay there long enough to cause damage.
Ladybirds are beloved by farmers and gardeners alike because they prey on numerous crop-eating pests. Aphids are ladybirds' favourite food, but they also like to eat soft-scale insects, mealybugs and spider mites, as well as the eggs of the Colorado Potato Beetle and European Corn Borer. According to Ohio State University researchers, some species consume plant and pollen mildews. Thanks to a large appetite and reproductive capacity, ladybug beetles often fully destroy pest populations.
Because of this voracious eating habit, ladybirds are sold by a number of gardening sources as a natural means of control, suitable for organic gardening as well as the movement toward green living.
Even though box elder bugs are not much more than a nuisance, many gardeners want to get rid of them, particularly if the area is close to a building. Taking a hose and dousing plants and trees with a forceful spray of water can rid box elder bugs from gardens.
Inexperienced gardeners might want to also rid ladybirds from their growing areas because of the recent American infestation of one species, the Asian Lady Beetle, which bites humans in the fall when it searches for a winter home. These bites are not harmful, merely annoying. As this variety also consumes pests, it's better to leave them in gardens during the growing season.